Rapid latensification of silver halide photographic materials



J. H. JACOBS Dec. 21, 1965 RAPID LATENSIFIGA'IION OF SILVER HALIDE PHOTOGRAPHIC MATERIALS Filed 001;. 26. 1962 INVENTOR Jflfl/VA M46035 ATraI/VA'VJ'.

United States Patent Ofltice 3,224,877 Patented Dec. 21, 1965 3,224,877 RAPID LATENSIFICATION F SILVER HALIDE PHOTOGRAPHIC MATERIALS John H. Jacobs, Altadena, Calif., assignor to Consolidated Electrodynamics Corporation, Pasadena, Calif., a corporation of California Filed Oct. 26, 1962, Ser. No. 233,311 3 Claims. (CI. 9627) This invention relates to increasing the writing speed of exposed silver halide emulsions of the develop-out type.

For the purposes of this application, silver halide emulsions utilized in photography can be divided into two classes: develop-out and print-out. Print-out emulsions are defined as those emulsions not requiring the application of an external medium in order to render the image visible. Develop-out emulsions are defined as those emulsions requiring the application of an external medium, such as a developing solution, in order to present a visible image. The term develop-out emulsion, as used herein, excludes those emulsions which contain a developer and which are responsive, upon the application of heat, to actuate the development process so as to present a visible image, such emulsions commonly being known as heat develop emulsions.

A wide variety of develop-out emulsion compositions are known and are commercially available. The present invention relates to those develop-out emulsions which are blue sensitive, i.e., emulsions which are sensitive to blue and ultra-violet radiations in the range of 3600 angstrom units to produce fogging of the invisible record when developed. It is, of course, understood that, if radiations within this range are of sufiicient intensity and duration, the exposure of the emulsion, to such radiations may produce, by massive photolysis, a visible image. However, such an exposure is not within the scope contemplated by the present invention. Rather, the intensity and duration of exposure contemplated is that radiation producing an invisible fogging of the record, which fogging subsequently becomes visible upon development of the emulsion. The recorded image conventionally exposed to such radiations and then developed is inferior in clarity to the image which would have been produced absent the fogging exposure.

According to the present invention, the fogging of a blue sensitive silver halide develop-out emulsion, having an image invisibly recorded therein, is prevented, while the writing speed of the emulsion is simultaneously increased, by heating the emulsion containing the invisibly recorded image to a temperature of about 250 degrees Fahrenheit, and substantially immediately thereafter exposing the emulsion to electromagnetic radiations of about 3600 angstrom units and of an intensity such as would fog the emulsion if the emulsion were subjected to such an exposure when at a temperature of about 75 degrees Fahrenheit, i.e., at room temperature.

The invention may be more readily understood by referring to the accompanying drawing which illustrates the utilization of the invention in the art of oscillography. In the drawing, a recording oscillograph 11 has an outer case 12. A galvanometer mirror 13 is connected to a galvanometer (not shown) so as to reflect light direct thereon from a conventional light source 14. The light source 14 is shown functionally and may be, for example, a conventional tungsten lamp whose radiations are collimated prior to falling upon the galvanometer mirror. The light reflected from the galvanometer 13 passes through an aperture in an inner dividing wall 16 of the oscillograph 11.

Photographic material consisting of a develop-out emulsion 17 supported on a backing (not shown) so as to be contained in a roll 18 passes from the roll 18 around a recording roller 19 positioned adjacent the aperture 15. The recorded radiations reflected from the galvanometer mirror 13 pass through the aperture 15 and fall upon the develop-out emulsion 17 at the recording roller 19. The develop-out emulsion 17 then passes around an idler roller 20 and onto a platen 21. The platen 21 contains heating means (not shown) operable to heat the platen at a temperature which is preferably about 250 degrees Fahrenheit. The heat from the platen 21 is transferred to the develop-out emulsion 17 through its backing, the backing contacting the surface of the platen 21 so as to separate the platen from the emulsion. A pair of radiation sources 22 are disposed above the platen 21 so that their radiations fall upon the emulsion 17 during the latter portion of its travel over the platen 21. The radiation sources 22 provide radiations of about 3600 angstrom units and may be, for example, fluorescent lamps of the conventional Black Light Blue type (BLB) manufactured by General Electric, Westinghouse, Sylvania, and others. Of course, it is understood that other sources of illumination with appropriate filtering may be used.

After leaving the platen 21, the develop-out emulsion 17 is carried between a drive roller 24 and a second idler roller 25. These two rollers 24, 25 provide the traction, by means of which the develop-out emulsion 17 is unrolled from the roll 18 and passed along the path just described. Upon passing through the rollers 24, 25, the emulsion 17 issues from an aperture 27 in the oscillograph outer case and is available for development processing. Such processing may be carried on in a processor of the type, for example, as is shown in United States Patent No. 2,952,201.

In the foregoing description, it was indicated that the platen was heated to a temperature of about 25 0 degrees Fahrenheit. This temperature is selected, for a rate of travel of conventional oscillographic paper over the heated platen of from one to forty inches per second. Such a rate provides sufiicient heat transfer, for a platen of about twelve inches in length, to prevent fogging. The elevation of the emulsion to a temperature which apparently inactivates the blue sensitivity of the emulsion to fogging, thus permits the exposure to the radiations to the Black Light Blue sources to increase the writing speed of the exposed emulsion.

It will, therefore, be understood that the essence of the invention resides in the exposure of the heated emulsion to the radiations which would otherwise fog the emulsion. The heating can, of course, be accomplished by structures other than by passing the emulsion over a heated platen. Thus, while the use of a heated platen is shown and is the preferred structure, the use of radiation heating, hot air, or various other conventional methods are appropriate and are within the scope of the invention.

It will, of course, be appreciated that the use of the Black Light Blue source provides a band of radiation rather than a single radiation wave length of 3600 angstrom units, the Black Light Blue lamp having a radiation intensity peak at about 3600 angstrom units. It is, therefore, to be understood that the use of the term 3600 angstrom units, with respect to the radiations, is illustrative of the particular band of radiations employed in the practice of the invention rather than constituting a limit as a particular wave length. By way of example of the type of oscillograph paper particularly adapted to use with the invention, the papers produced by Ansco-Grant under the names Linatrace G4, Linatrace G-5 and Linatrace R-4 are appropriate. These papers have blue-sensitive emulsions rather than dye-sensitive emulsions. Of the three, Linatrace G4 and G5 are the slower in speed and therefore are preferable. Of these two papers,

Linatrace G-4 has a thinner backing than Linatrace G-S, and so provides certain advantages with respect to handling.

The invention claimed is:

1. A method for increasing the writing speed of a silver halide develop-out emulsion of the recording type which is blue sensitive to fogging and on which information has.

been invisibly recorded by exposure to electromagnetic radiations, comprising the steps of heating the emulsion to a temperature which inactivates its blue sensitivity to fogging, substantially immediately thereafter exposing the emulsion to radiations having wave lengths Within the blue sensitivity to fogging range of the emulsion, the radiations being limited to such a duration and intensity as only invisibly fog the emulsion When so exposed at a temperature of about 75 degrees Fahrenheit and thereafter subjecting the emulsion to development processing.

2. A method for increasing the writing speed of an oscillographic recorder using a silver halide emulsion of the develop-out type which is blue sensitive to fogging and on which information has been invisibly recorded by means of exposure to electromagnetic radiations, comprising the steps of heating the emulsion to a temperature of about 250 degrees Fahrenheit, substantially immediately there after, While at said temperature, exposing the emulsion to radiations having wave lengths of about 3600 angstrom units, the radiations being limited to a duration and intensity which would invisibly fog the emulsion When so exposed at a temperature of about 75 degrees Fahrenheit and thereafter subjecting the emulsion to chemical development.

3. A method for increasing the Writing speed of oscillographic recording paper having a silver halide emulsion of the develop-out type which is blue sensitive to fogging and is supported on a thin flexible backing, comprising the steps of invisibly recording information on said emulsion by means of electromagnetic radiations, heating a platen to a temperature of about 250 degrees Fahrenheit, passing the emulsion over the heated platen so that the backing separates the emulsion from the platen and at a rate such that a given portion of the emulsion contacts the platen for at least about 0.3 second to heat the emulsion, exposing the heated emulsions to radiations from a Black Light Blue fluorescent source, the radiations being limited to a duration and intensity such as would invisibly fog the emulsion when so exposed at a temperature of about 75 degrees Fahrenheit and thereafter subjecting the emulsion to chemical development to produce a visible image.

References Cited by the Examiner Dybvig et al.: Photographic Engineering, vol. 5, No. 2, pages 127 to 132, 1954.

Jacobs J. H., Photographic Science and Engineering, vol. 5, N0. 1, pages 1 to 4, January-February, 1961.

NORMAN G. TORCHIN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,224,877 December 21, 1965 John H. Jacobs It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 14, for "as only" read as would only Signed and sealed this 6th day of December 1966.

( L) Attest:

ERNEST W. SWTDER Attesting Officer Commissioner of Patents EDWARD J. BRENNER 

1. A METHOD FOR INCREASING THE WRITING SPEED OF A SILVER HALIDE DEVELOP-OUT EMULSION OF THE RECORDING TYPE WHICH IS BLUE SENSITIVE TO FOGGING AND ON WHICH INFORMATION HAS BEEN INVISIBLY ARECORDED BY EXPOSURE TO ELECTROMAGNETIC RADIATIONS, COMPRISING THE STEPS OF HEATING THE EMULSION TO A TEMPERATURE WHICH INACTIVATES ITS BLUE SENSITIVITY TO FOGGING, SUBSTANTIALLY IMMEDIATELY THEREAFTER EXPOSING THE EMULSION TO RADIATIONS HAVING WAVE LENGTHS WITHIN THE BLUE SENSITIVITY TO FOGGING RANGE OF THE EMULSION, THE RADIATIONS BEING LIMITED TO SUCH A DURATION AND INTENSITY AS ONLY INVISIBLY FOG THE EMULSION WHEN SO EXPOSED AT A TEMPERATURE OF ABOUT 75 DEGREES FAHRENHEIT AND THEREAFTER SUBJECTING THE EMULSION TO DEVELOPMENT PROCESSING. 